Organo-siloxanes and method of making them



Patented Dec. 28, 1948 UNITED STATES PATENT "orncr.

ORGANO-SILOXANES AND METHOD OF MAKING v THEM James Franklin Hyde,Corning, N. Y., assignor to Corning Glass Works, Corning, N. Y., acorporation oi New York No Drawing. Application December 15, 1943,Serial No. 514,410

This invention relates to new compositions of matter and theirpreparation and, moreparticularly, to organo-slloxanes and methods ofpreparing them.

The present application is a continuation-inpart of my copendingapplications Serial Number 432,528 filed February 26, 1942, SerialNumber 467,146 filed November 27, 1942 and Serial Number 503,159 filedSeptember 20, 1943, said,

. which is attached to silicon by other than carbonsilicon linkages andwhich under the same set of conditions is more readily hydrolyzed thanan organic radical directly attached to silicon through carbon-siliconlinkage. Such organosilanes may be hydrolyzed and dehydrated, the

4 Claims. (Cl. 260-448.2)

although crystalline polymers may be isolated .in some instances.

dehydration probably proceeding to some extent concurrently with thehydrolysis, particularly if the temperature is allowed to rise.

The formation of a siloxane linkage requires the close approach of twohydroxyl groups and subsequent elimination of water. It may also resultfrom the close approach of one hydroxyl group to a hydrolyzable groupsuch as halogen, acyloxy, or alkoxy and subsequent elimination of ahydrogen halide, a carboxylic acid or an alcohol respectively. Such'eliminations are catalyzed by mineral acids, especially hydrochloric andsulphuric acids, and alkali-metal hydroxides, especially sodiumhydroxide.

In each of the above structural units two of the four silicon bonds areshown blocked by the organic radicals R and R, and only two siloxanelinkages are possible. Hence a three-dimensional network is no longerpossible, and the resulting organo-siloxanes can comprise only chain andcyclic structures. Intermediate crystalline dihydroxy compounds can insome instances be isolated. The final products are usually liquids,

Organo-silanes of the type RR'RJ"S1X, when hydrolyzed and-dehydrated,yield very simple oxides in the structural unit of which three of the'four silicon bonds are blocked by the organic radicals R, R and R".

R! -R! R! R! I i a l I R-Si-X R-Sll-OH a-si-o-sl-a I! II I I! In thiscase, ease of hydrolysis is further diminished and in some cases theintermediate hydroxy silanescan be isolated. The completely dehydratedproduct is dimeric because only one siloxane linkage can be formed. Thedimers are either crystalline or liquid.

Prior attempts to utilize the above-described reactions have notcontemplated combinations thereof, but have been confined more or lessto the individual reactions and their products. Such products, as shownabove, have limited utility and the range of properties obtainable inthe products of a given type of reaction is relatively restricted. Forexample, the hexa-organo-disiloxanes are generally inert liquid productswhich, although they are soluble in organic solvents, cannot becondensed beyond the dimer.

An object of this invention is the production of new and useful productsfrom these reactions which will have desirable predetermined properties.

Another object is to combine the above-described reactions and thus tointer-condense the hydrolysis products of di-organo-substituted-'silanes and tri-organo-substituted silanes.

Another object is to produce liquid products of varying viscosity.

Another object is to produce polymeric liquid products which possessgreat resistance to fur,- ther polymerization.

A still further object of the present invention is to provide a methodof preparing an organosiloxane which comprises essentially oxygen atomsand organo-silicon units which correspond to the general formulae andsaid units being connected by said oxygen atoms through silicon-oxygenlinkages, where R, R,

R", R', and R"" represent the same or different organic radicalsattached to silicon through carbon-silicon linkages.

Another object of my invention is to prepare organo-siloxanes comprisingessentially oxygen atoms and organo-silicon units which correspond tothe general formulae m I R 1 m where R, R, R", R."" and R" arehydrocarbon radicals and n is an integer.

The new method comprises mixing at least one silane of the generalformula RR'SiXY with at least one silane of the general formula R!!!R"-SiZ where R, R, R", R' and R"" are the same or different organicradicals and X, Y, and Z are the same or difierent hydrolyzable radicalsand causing them to hydrolyze together and to become inter-condensed. Itis to be understood that each of the silanes is present in appreciablequantity, i. e. in amount sufiicient to produce a perceptible effect inthe resulting inter-condensate. One method of accomplishing this is byintroducing into the mixture by dropwise addition thereto the amount ofwater which is calculated for complete hydrolysis of the mixture andwhich preferably is dissolved in from two to four volumes of a commonsolvent such as alcohol, dioxan, acetic acid, acetone, etc. Although adifference in the reactivity of the various individual types ofhydrolyzable compounds and a variation in the amounts present in theinitial mixture may make it desirable to vary the conditions of theprocess, as will appear from a consideration of the accompanyingexamples, the above recited procedure in general is to be preferred. Theuse of a water miscible solvent for diluting the hydrolyzable mixture orthe water or both and the dropwise addition of the water insures themaintenance of homogeneity during hydrolysis. Under these conditionscondensation or the formation of siloxane linkages occurs concurrentlywith the one hydrolyzable tri-organo-substituted-silane,

hydrolysis and dehydration by my method will result ininter-condensation or formation of inter-connecting oxygen linkagesbetween the silicon atoms of thevarious silanes. The variety of thesubstituted organic radicals is limited only by their ability to form aGrignard reagent. In other words, the organo-silanes which may beemployed in my process include all such compounds which contain one ormore hydrolyzable atoms or groups and which may be prepared by means ofthe well-known Grignard reaction. The radicals which may thus besubstituted may include alkyl radicals such as methyl, ethyl, propyl,isoproply, butyl, iso-butyl, amyl, hexyl, heptyl to octadecyl andhigher; alicyclic radicals such as cyclopentyl, cyclohexyl, etc.; aryland alkaryl radicals such as phenyl, monoand poly-alkyl phenyls as totolyl, xylyl, mesityl, mono-, di-, and tri-ethyl phenyls, mono-, di-,and tri-propyl phenyls, etc.; naphthyl, monoand poly-alkyl naphthyls, asmethyl naphthyl, diethyl naphthyl, tripropyl naphthyl, etc.;tetra-hydronaphthyl, anthracyl, etc.; aralkyl such as benzyl,phenylethyl, etc.; alkenyl such as methallyl, allyl, etc. The aboveradicals may contain inorganic sub stituents such as halogens, etc.

If the hydrolyzable group or groups of all of the silanes in the mixtureto be hydrolyzed are halogens, it is preferable to employ dioxan as thesolvent because it is inert to the halogens. If the mixture containsboth halogens and alkoxy groups, the former can be converted to thelatter by the slow addition of dry alcohol to the mixture, or themixture can be diluted with dioxan and I treated with aqueous alcohol.When the mixture contains only alkoxy groups any water miscible Isolvent may be used together with a trace of acid such as HCl ascatalyst. In this case, alcohol may be preferred on account of itsrelatively low cost. Mixtures of water miscible solvents may be used.

In the above-described method, the slow incorporation of water into thehomogeneous solution insures that hydrolysis is not permitted to proceedunchecked, whereby the more reactive silane or silanes, would be morecompletely hydrolyzed and condensed before the less reactive silaneshave had an opportunity to react. On the contrary, the less reactivesilanes are thus given a greater opportunity to hydrolyze simultaneouslywith the more reactive silanes than would be the case if the hydrolysiswere conducted rapidly. Under these circumstances, simultaneouscondensation of the various intermediate hydroxy compounds takes placeand an intimate inter-molecular combination through siloxane linkages ofsilicon atoms bearing different numbers and kinds of organic radicalsbecomes possible to the fullest extent. This insures a trueinter-condensation with the formation of homogeneous products containingmixed unit structures.

After removal of solvent and excess water the hydrolysis productsresulting from the above process are Water-immiscible liquids of varyingviscosity. They are soluble in the common organic solvents such asbenzene, toluene, etc. They vary in the extent to which dehydration hasoccurred at this stage. The ease of further dehydration depends upon thekind of substituted organic radicals and upon their number or upon thefinal ratio of oxygen to silicon. Subsequent heating is usuallynecessary for complete dehydration. Products containing methyl radicalsdehydrate more readily than those containing ethyl, propyl, etc.,radicals or phenyl radicals and in general products containing alkylradicals dehydrate more readily than those containing aryl radicals. Theextent of further dehydration also depends upon the percentage oftri-organo-silicyl units present, the greater the amount of thetriorgano-silicyl units present the fewer hydroxyl groups that areavailable to take part in subsequent condensation reactions.

In general. the completely dehydrated products are thermally stable or"permanent liquids, that is, they are liquids which are incapable offurther change by condensation. They comprise linear polymers whose endsare blocked by tri-organosilicyl units. Polymerization of these polymerscan only be accomplished by removal of groups or by rupture of 81-0linkages. both of which require special treatment. The viscosity of theproducts may be controlled by regulating the relative proportions ofdiand tri-organo-silicyl units, the greater the percentage ofdi-organosilicyl units, the higher the resultant viscosity.

The following examples will illustrate the mode of operation of theprocess and the character of the resulting products. In the examples,the starting compound (CsH5)(CHa)2SiCl was prepared by silicontetra-chloride by the action of the phenyl and methyl Grignard reagentsunder substantially anhydrous conditions. Fractional distillation of thereaction product yielded (CsHtHCHslnSiCl boiling at 79 C. at mm.pressure. The starting compound EXAMPLEI 1 Equim'olecular parts oi(CoHs) (CHahSlCl and (CH3)2S1(OC2H5)2 were mixed and treated dropwisewith the calculated amounts of water for complete hydrolysis dilutedwith four volumes of alcohol. 0n evaporation of solvent a mobile liquidremained which was unchanged by heating and which performedsatisfactorily as a transformer oil.

Composition: O/Si=0.75

EXAMPLE2 Two equivalents of (CeHs) (CH3)SiCl2 and one oi (Cal-Is)(CHalzSiCl were mixed and diluted with ,dioxane. An amount of waterslightly in excess of thecalculated quantity was slowly added. On

'dilution'with water after completion of the inter-' and 95% ethylalcohol was added. The mixture was heated and then diluted with water.The product was a homogeneous oil having useful lubricating properties.

' Composition: 0/81: .975

condensation, the product was precipitatad as an oil.

Composition: 0/Si=0.83

EXAMPLE 3 EXAMPLEQ To a solution of (CH3)3S1(OC2H5) tions 1/2 was addedslowly ethyl alcohol to effect hydrolysis and inter-condensation.

Water was then added in slight excess. After boiling of! the solvents,an oily liquid remained.

Composition. O/Si=0.83

EXAMPLE 5 To a solution of (CiiH5'CH2)(CoH5)S iC12 and (CHa)aS1(OC2H5)in the molar proportions 1/2 was added slowly 95% ethyl alcohol toeffect hydrolysis and inter-condensation. Water was then added in slightexcess. After boiling off the solvents, the concentrated product was aslightly viscous liquid.

- Composition: 0/Si=0.67

EXAMPLE 6 EXAMPLE 7 As in the previous example (CH3)2S1(OC2H5)2 and(CH3)3Si(OC2H5) were cohydrolyzed and inter-condensed, except that themolecular proportions were 10/1 respectively. A liquid product ofsomewhat higher viscosity and boiling range than that in the previousexample was obtained.

Composition: O/Si=0.95

EXAMPLE 8 To a solution of (CeH5-CH2)3S1C1 and (CH3)2S1(OC2H5)2 in themolar proportions 1/5 was added slowly 95% ethyl alcohol to effecthydrolysis and intercondensation. Water was then added in slight excess.After boiling off the solvents, theconcentrated product was a ratherviscous liquid.

Composition; o s1=o.92

For many uses, particularly in .iluid pressure operated devices, itispreferred to use instead of .the above mixtures of polymers having arange of physical properties, an individual polymer of having thedefinite physical properties of a pure chemical compound where the Rsrepresent the same or diflerent hydrocarbon radicals. These may beobtained by isolation of the individual members from the hydrolysate ofa mixture of msix and R2SiX2 which is prepared in such a manner as to besubstantially completely hydrolyzed and free from cyclic polymers of theformula (R2SlO)x. This is illustrated by Example 9 which shows thepreparation of a random mixture of polymers belonging to the series thespecies and (CH2=C(CH3)CH2)2S1C12 in the molar proporvacuum and theseparation of the individual members EXAMPLE 9 In a liter three-neckedflask, fitted with a reflux condenser, agitator and thermometer, wereplaced 1393 grams (9.41 mol) of redistilled (CH3)2Si(OC2H5)-2 and 1110grams (9.411 mol) of (CHahSiOCzI-Is. To this solution was added 254grams (10.11 mol) of water containing 7.5.grams of NaOH, (approximately1 NaOI-I per 100 silicon atoms). This insured the formation of onlystraight chain polymers. The mixture was heated to 40 C. and thetemperature continued to rise for nearly an hour. After adding 50 cc.(20% excess) more water, the mixture was refluxed for 2 hours and thenallowed to stand overnight.

Alcohol was then distilled ofi, until the temperature reached 100 C.1706.6 grams of distillate was collected. (Theory 1430 grams.) Thisalcohol was poured into four times its volume of water and an insolubleoii separated (45"! grams). The insoluble fraction was added back to the8 of from 125 to 215 C. at 0.125 mm. Refractionation of this distillateshowed it to be composed of members of the above series where n is 3 to13 inclusive. That is, it consisted Of intercondensates of (CH3):4S1Owith CH: I

containing from 10 to 15 silicon atoms inclusive. The properties ofthese materials are shown in ,Table 1, section B. An undistilled residueof 39.1

rams remained. This was treated with decolorizing carbon and filtered togive the final residue as shown in the following Table I, section C.Evidently, this residue contained linear polymers having more than 15silicon atoms in the molecule.

TABLE I Physical properties of trimethylsilicyl end blocked dimethylsiloxane polymers silicon oils were carefully washed with distilledwater until neutral. The yield was 1426 grams (Theory 1469 grams).

The oil was distilled in a fractionating column packed with glasshelices, first at atmospheric pressure. then at reduced pressure. Thefractions from the plateaus in the distillation curve were fractionatedand the properties of the pure siloxane polymers were determined. Theseare shown in the data of Table 1, section A from which it appears thatthe individual fractions are members of the series copolymer residuefrom the distillation and 555 25 L i cc. of 20% hydrochloric acid wasadded. The E4 1 5 1 c ti o 11 1 005 y 1 en S R f 1 09 .9

pec C 8 3S1 igi g B. P C. stokes Gravity Index Point, ggf

- at 25 C. at 25 0 F CJXNH 0.65 1.76 .7000 1. 3748 15 1.50 1.04 2. 0701142 1. 3322 03 1. 451 1.33 .2 10 1. 3372 15s 1. 312 10 1. 002 2021.247 secflmA 0 2.03 0.67 .3573 1.3022 245 1.200 3. 24 12. 50 .0004 1.3040 272 1.154 3. s3 10. 40 .0073 1. 3052 202 1. 4. 5s 10. 00 .01401.3003 310 1.110 5.35 23. 5 .0002 1.3073 350 1.073 0. 10 2s. 3 .0247 1.3002 371 1. 055 305001113 177 0.5mm 0.35 33.2 .0234 1.3000 330 1.034 10205 mm 7.75 38.0 .0317 1.3003 400 1.010 207 05 mm 8.70 44.3 .0314 1.4004422 .000 222 05 mm 0.05 50.5 .9368 1.4010 437 .033 SectionC 12.0 03.0.0454 1.4003 453 acid mixture was refluxed for two hours, and the I t ePreparation of m t es of ol cular species having the general formulaRSi-O- SiO]-S1R1 it is apparent that the average Value of n will dependin general upon several factors which include (1) the molecular ratio ofR"-S iZ i X-Si-Y radicals.

preparations may contain linear molecules of the general formuladrolysis to replace X with OK and condensation to form r r R mslo 8|i-0i Si-Si-0 1-0 Bill;

or (2) interaction with RaSiOH or (3) conjoint hydrolysis andinter-condensation in the presence of RsSiZ.

It will be seen that the inter-condensates produced by my method are notmixturesoi individual organo-siloxaiies but are new compounds difieringtherefrom in homogeneity of structure and. properties. It will furtherbe seen that the new oraanmsilozanes may contain various difierentradicals attached to the same silicon atom and the individual siliconatoms may difler in the number and hind oi radicals attached thereto, inwhich respect the new slloxanes difler from previous siloxanes whereeach silicon atom was attached to the same kind and number of Suchdifferences result in new compounds or inter-condensates which embodyvarious improvements over previous organo-siloxanes with respect totemmrature coemcient of change of viscosity, thermal resistivity,chemical stability, electrical properties, etc.

The organo-siloxanes produced by my method may be adapted to varioususes and for any specific use the physical properties andcharacteristics of the product can be controlled by-the proper selectionof the initial starting materials so as to obtain the desired oxygen tosilicon ratio and a suitable variety of radicals attached to the siliconatom. Some of the products have good electrical properties whereby theymay be used as the liquid filling medium for transformers, circuitbreakers, submarine cables, condensers, etc. In general the productshave an unusually low coemcient of change of viscosity with temperatureand flnd use in hydraulic pressure systems which are subjected to widechanges of temperatures or as lubricants for systems of moving partsoperating under subnormal or abnormal temperatures.

10 I claim: 1. Liquid organopolysiloxanes corresponding to the formulaRI RI! where R, R and R" each represents a. monovalent hydrocarbonradical, at least one R and at least one B" each representing a phenylradical, and

n represents a positive integer.

Liquid organopolysiloxanes corresponding to the formula where Rrepresents a phenyl radical, R represents a lower alkyl radical, and nrepresents a positive integer.

3. Liquid organopolysiloxanes corresponding to the formula where nrepresents a positive integer.

4. Liquid organopolysiloxanes corresponding to the formula R B. R" R--8l 0S i 0-SiR" R/. L i! l I n where R, R. and R each represents amonovalent hydrocarbon radical, at least one B and at least one B." eachrepresenting a benzyl radical, and

n represents a positive integer.

JAMES FRANKLIN HYDE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS pages 325-328. V

Keppinm-Joun'chem. Soc., (London) vol. '79, mes 455-458.

Martin, "Jour. Chem. 800.," (London) vol. 95, pages 807-309.

